Electronic circuit unit and its sealed structure

ABSTRACT

A first frame is arranged on a printed circuit board to enclose a first circuit that radiates a noise. The printed circuit board also has mounted thereon a second circuit that has a need to be protected from the noise. A second frame is arranged on the printed circuit board to enclose the second circuit. The second frame is separated from one side of the first frame by a given clearance area, and the second frame has an open side facing the one side of the first frame.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Division of application Serial No. 11/089,910,filed Mar. 24, 2004, which is based upon and claims the benefit ofpriority from prior Japanese Patent Application No. 2005-82377, filedMar. 22, 2005, the entire contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electronic circuit unit built insmall-sized electronic apparatuses such as mobile phones and PDA(Personal digital Assistants), and to its shield structure.

2. Description of the Related Art

In general, small-sized electronic apparatuses such as mobile phones andPDA have a built-in electronic circuit unit, which is mounted with manycircuit devices on a printed circuit board. The circuit devices includethe following circuit device groups. One is a circuit device group suchas CPU (Central Processing Unit) and DSP (digital signal Processor)radiating a noise. Another is a circuit device group such as radiocircuit, which is easy to receive an influence by noise. In theforegoing circuit device groups, the noise radiated from the circuitdevice group such as CPU gives an influence to the circuit device groupsuch as radio circuit depending on the positional relationship. As aresult, this is very unfavorable because radio transmitting andreceiving performance is reduced.

Conventionally, the following structure has been employed. For example,two frames produced by sheet metal processing are prepared. The circuitdevice group radiating the noise is enclosed with one of two frames; onthe other hand, the circuit device group readily receiving the influenceby noise is enclosed with the other thereof. The structure describedabove is given, and thereby, each frame functions as a shield case;therefore, the influence by the noise is reduced between the foregoingcircuit device groups.

However, if the foregoing two frames are located separately from eachother, a clearance area for repair must be secured between these frames.For this reason, these frames must be arranged with a given distance ormore. As a result, the electronic circuit unit is inevitably configuredinto a large size. This is difficult to meet the requirements such asminiaturization of electronic apparatus and high packaging density ofcircuit device resulting from high function of apparatus.

Moreover, the shield structure given below has been proposed. Accordingto the shield structure, a partition plate is provided in a rectangularframe to form two independent rooms. The foregoing two rooms eachreceive the circuit device group radiating the noise and the circuitdevice group readily receiving the influence by noise. The technique isdetailedly disclosed in JPN. PAT. APPLN. KOAKI Publication No.2001-144487.

However, according to the foregoing shield structure, the frame isconfigured to a large size. If the frame is produced using sheet metalprocessing, the flatness of the frame is reduced. This is a factor ofcausing packaging failure when the frame is mounted on a printed circuitboard. Moreover, if the upper opening portion of the frame is attachedwith a cover, the frame and the cover are formed into a large size; forthis reason, a gap is readily formed between the frame and the cover.This is a factor of reducing the uniformity of isolation characteristicbetween circuit devices.

BRIEF SUMMARY OF THE INVENTION

The present invention has been made in view of the foregoingcircumstances. An object of the present invention is to provide anelectronic circuit unit, which prevents a reduction of packaging qualityby the scale-up of a frame, and enables high density of device packagingwhile securing a necessary clearance area, and to its shield structure.

In order to achieve the foregoing object, according to one aspect of thepresent invention, there is provided an electronic circuit unit and itsshield structure. A first frame is arranged on a printed circuit boardmounted with a first circuit radiating a noise and a second circuithaving a need to protect it from the noise to enclose the first circuit.A second frame is prepared in a state of removed one of several sidesforming the frame, which is faces the side of the first frame. Thesecond frame is arranged on the printed circuit board to enclose thesecond circuit with a given clearance area with respect to one side ofthe first frame.

Additional objects and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and obtained by means ofthe instrumentalities and combinations particularly pointed outhereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention, andtogether with the general description given above and the detaileddescription of the embodiments given below, serve to explain theprinciples of the invention.

FIG. 1 is a perspective view showing the shield structure of a firstshield case of an electronic circuit unit according to one embodiment ofthe present invention;

FIG. 2 is a perspective view showing the shield structure of a secondshield case of the electronic circuit unit according to one embodimentof the present invention;

FIG. 3 is a top plan view to explain the relationship in arrangementbetween the first and second shield cases of the electronic circuit unitaccording to one embodiment of the present invention;

FIG. 4 is a top plan view to explain the electronic circuit unit shownin FIG. 1 to FIG. 3 and the effect of the shield structure;

FIG. 5 is a top plan view to explain the electronic circuit unit shownin FIG. 1 to FIG. 3 and the effect of the shield structure;

FIG. 6 is a perspective view showing the shield structure of a secondshield case of the electronic circuit unit according to anotherembodiment of the present invention; and

FIG. 7 is a cross-sectional view to explain the relationship inarrangement between the first shield case of the electronic circuit unitaccording to one embodiment of the present invention and the secondshield case shown in FIG. 6.

DETAILED DESCRIPTION OF THE INVENTION

An embodiment of the present invention will be described below withreference to the accompanying drawings.

An electronic circuit unit according to one embodiment of the presentinvention includes first and second shield cases. The first shield casereceives circuit devices radiating a noise, and the second shield casereceives circuit devices having a need to protect them from the noise.

The circuit devices radiating a noise include circuit devices forming adigital circuit such as CPU (Central Processing Unit) and DSP (DigitalSignal Processor). On the other hand, the circuit devices having a needto protect them from the noise include high frequency circuit devicessuch as LSI (Large Scale integrated Circuit) forming a radio circuit.

As shown in FIG. 1, the first shield case is composed of a metal frame 1and a metal cover 2 attached to the metal frame 1. The metal frame 1comprises a rectangular frame having four sides 11 to 14, and isproduced using sheet metal processing. A pair of mutually opposed sides11 and 13 of the metal frame 1 is connected via a bridge member 15. Thebridge member 15 functions as a reinforcement member for protecting themetal frame 1 from deformation. The bridge member 15 is provided with anadsorption member 16 at the central portion. The adsorption member 16 isused for lifting up the metal frame 1 by a robot arm when the metalframe 1 is mounted on a printed circuit board 10.

The metal frame 1 is positioned and fixed on the printed circuit board10 to enclose circuit devices (not shown) radiating a noise. Solderingis used as the fixing means. In FIG. 1, reference numerals 17 denote thesoldering pattern.

The metal cover 2 is produced using sheet metal processing like themetal frame 1. The metal cover 2 closes the metal frame 1 so that noiseradiated from circuit devices received in the metal frame 1 does notexternally leak from there. The metal cover 2 is attached to the upperopening portion of the metal frame 1.

As illustrated in FIG. 2, the second shield case is composed of a metalframe 3 and a metal cover 4 attached to the metal frame 3. The metalframe 3 is produced using sheet metal processing in a manner that one offour sides forming a rectangular frame is removed. A pair of mutuallyopposed sides 31 and 33 of the metal frame 3 is connected via a bridgemember 35. The bridge member 35 functions as a reinforcement member forprotecting the metal frame 3 from deformation. The bridge member 35 isprovided with an adsorption member 36 at the central portion. Theadsorption member 36 is used for lifting up the metal frame 3 by a robotarm when the metal frame 3 is mounted on a printed circuit board 10 likethe metal frame 1 described before.

The metal frame 3 is positioned and fixed on the printed circuit board10 to enclose circuit device groups 6 having a need to protect them froma noise. Soldering is used as the fixing means. In FIG. 2, referencenumerals 37 denote the soldering pattern.

The metal cover 4 is produced using sheet metal processing like themetal frame 3. The metal cover 4 closes the metal frame 3 to prevent anoise radiated from circuit devices received in the metal frame 1 fromintruding into the metal frame 3 and from giving an influence to thecircuit device group 6. The metal cover 4 is attached to the upperopening portion of the metal frame 3.

The foregoing metal frames 1 and 3 are arranged on the printed circuitboard 10 in the following manner. FIG. 3 is a top plan view to explainthe arrangement relationship. More specifically, the metal frame 3 isarranged so that the removed side is opposed to the side 12 of the metalframe 1. In this case, the metal frame 3 is positioned opposing to themetal frame 1 with a distance L2. The distance L2 is given, and thereby,a clearance area is secured between the metal frames 1 and 3. Theclearance area is used for repairing packaging (mounting) failurerelevant to the metal frames 1 and 3.

As described above, one side of the metal frame 3 forming the secondshield case is removed. By doing so, the clearance area required forrepair is secured between the metal frames 1 and 3 while the packagingdistance of circuit devices 5 and 6 is made small. As a result, circuitdevice packaging density is enhanced in the printed circuit board 10having a limited packaging area. In other words, it is possible to meetthe requirements such as miniaturization and high packaging density inthe electronic circuit unit.

For example, metal frames 1 and 7 formed into a frame shape are used asthe first and second shield cases, respectively, as depicted in FIG. 4.In this case, the packaging distance must be set considering thethickness of the sides of both metal frames 1 and 7 as seen from a widedistance L3 in FIG. 4. This is a factor of causing a reduction of thepackaging density.

According to this embodiment, the metal frames 1 and 3 are producedseparately from each other. Thus, the flatness of these metal frames 1and 3 is enhanced. As a result, it is possible to reduce packagingfailure cased when the metal frames 1 and 3 are mounted on the printedcircuit board 10. This contributes to improving the yield and the shieldeffect.

Moreover, the metal covers 2 and 4 are produced separately from eachother. Thus, the flatness of these metal covers 2 and 4 is enhanced. Asa result, a gap is hard to be formed between the frame and cover in astate that the covers 2 and 4 are attached to the metal frames 1 and 3.Therefore, this contributes to enhancing uniformity in isolationcharacteristic between circuit devices 5 and 6.

If the first and second shield cases are each composed of onerectangular frame and its cover, the frame and the cover are formed intoa large scale. For this reason, the flatness of the frame and the coveris reduced. As a result, a gap is readily formed between the frame andthe printed circuit board and between the frame and the cover. This is afactor of reducing isolation characteristic between circuit devices.

For example, a rectangular metal frame 8 having four sides 81 to 84 isprepared as seen from FIG. 5. A partition plate 85 is provided in themetal frame 8 to form two independent rooms 86 and 87. These rooms 86and 87 receive a circuit device group radiating a noise and a circuitdevice group easy to receive an influence by noise, respectively. InFIG. 5, a reference numeral 9 denotes a metal cover, and a referencenumeral 88 denotes a soldering pattern for mounting the metal frame 8 ona printed circuit board.

If the foregoing shield case is produced using sheet metal processing,both frame 8 and cover 9 are made into a large scale. For this reason,the flatness is reduced; as a result, uniformity of isolationcharacteristic is not obtained as described before.

According to this embodiment, mutually opposing sides of the metalframes 1 and 3 are connected via the bridge members 15 and 35.Therefore, the structural strength of these metal frames 1 and 3 isenhanced, thereby reducing packaging failure of the metal frames 1 and 3and enhancing the shield effect. Moreover, it is possible to improve thereliability of an electronic circuit unit.

According to this embodiment, the foregoing bridge members 15 and 35 areprovided with the adsorption members 16 and 36, respectively. Thus,these metal frames 1 and 3 are lifted up using a robot arm when mountingthem on the printed circuit board 10. By doing so, the metal frames 1and 3 are automatically mounted.

The present invention is not limited to the foregoing embodiment. Forexample, at least one of the metal covers 2 and 4 shown in FIG. 1 andFIG. 2 may be provided with an extended portion. For example, as shownin FIG. 6, a cover 40 including an extended portion 41 may be attachedto the metal frame 3 according to another embodiment of the presentinvention. The extended portion 41 comprises a flange or protrusion.When the metal covers 2 and 40 are attached to the metal frames 1 and 3,the extended portion 41 is overlapped with the metal cover 2, as shownin FIG. 7. The structure described above is given, and thereby, themetal covers 2 and 40 are electrically integrated. This serves tofurther enhance the shield effect. The metal cover 40 may be attached tothe metal frame 1 instead of to the metal frame 3.

In the foregoing embodiment, the metal frames 1 and 3 each comprise arectangular shape having four sides. In this case, the metal frames 1and 3 may each comprise a polygon frame having four sides or more. Ifseveral sides of the metal frame 1 are opposed to those of the metalframe 3, these opposed sides may be removed.

Besides, various modifications of the features given below may be madewithin the scope without diverging from the subject matter of thepresent invention. The features are as follows:

Structure and shape of the printed circuit board;

Shape and structure of first and second frames and covers;

Presence, position and shape of the bridge member; and

Kind of a first circuit radiating a noise and a second circuit having aneed to protect it from the noise

In short, the present invention is not limited to the foregoingembodiment. In the wording stage, components may be modified within thescope without diverging from the subject matter of the invention.Several components disclosed in the foregoing embodiment are properlycombined, and thereby, various inventions are formed. For example, somecomponents may be deleted from all components disclosed in theembodiment. Components relevant to different embodiment may be properlycombined.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

1. (canceled)
 2. An electronic circuit unit comprising: a printedcircuit board mounted with a first circuit that radiates a noise and asecond circuit that has a need to be protected from the noise; a firstframe arranged on the printed circuit board around the first circuit; asecond frame arranged on the printed circuit board around the secondcircuit, said second frame being separated from one side of the firstframe by a given clearance area, and said second frame having an openside facing the one side of the first frame; a first cover which closesan upper opening portion of the first frame; and a second cover which isindependent of the first frame, and which closes an upper openingportion of the second frame; wherein at least one of the first andsecond covers comprises an extended portion that overlaps the other ofthe first and second covers.
 3. The unit according to claim 2, whereinat least one of the first and second frames comprises a bridge memberextending between opposing sides thereof.
 4. The unit according to claim3, wherein the bridge member comprises an adsorption member for liftingup the frame.
 5. (canceled)
 6. A shield structure comprising: a firstframe arranged on a printed circuit board around a first circuit thatradiates a noise, said printed circuit board also having mounted thereona second circuit that has a need to be protected from the noise; asecond frame which is arranged on the printed circuit board around thesecond circuit, said second frame being separated from one side of thefirst frame by a given clearance area, and said second frame having anopen side facing the one side of the first frame: a first cover whichcloses an upper opening portion of the first frame; and a second coverwhich is independent of the first frame, and which closes an upperopening portion of the second frame; wherein at least one of the firstand second covers comprises an extended portion that overlaps the otherof the first and second covers.
 7. The structure according to claim 6,wherein at least one of the first and second frames comprises a bridgemember extending between opposing sides thereof.
 8. The structureaccording to claim 7, wherein the bridge member comprises an adsorptionmember for lifting up the frame.
 9. An electronic circuit unitcomprising: a printed circuit board mounted with a first circuit and asecond circuit; a first frame arranged on the printed circuit boardaround the first circuit; a second frame arranged on the printed circuitboard around the second circuit, said second frame being separated fromone side of the first frame by a given clearance area, and said secondframe having an open side facing the one side of the first frame; afirst cover which closes an upper opening portion of the first frame;and a second cover which is independent of the first frame, and whichcloses an upper opening portion of the second frame; wherein at leastone of the first and second covers comprises an extended portion thatoverlaps the other of the first and second covers.
 10. A shieldstructure comprising: a first frame arranged on a printed circuit boardaround a first circuit, said printed circuit board also having mountedthereon a second circuit; a second frame arranged on the printed circuitboard around the second circuit, said second frame being separated fromone side of the first frame by a given clearance area, and said secondframe having an open side facing the one side of the first frame; afirst cover which closes an upper opening portion of the first frame;and a second cover which is independent of the first frame, and whichcloses an upper opening portion of the second frame; wherein at leastone of the first and second covers comprises an extended portion thatoverlaps the other of the first and second covers.